Variable exhaust system for combustion engine

ABSTRACT

An exhaust system is disclosed with movable elements to accommodate various operating states of an associated engine. In one embodiment a diverging megaphone faces a reflector which may be variously positioned in relation to the end of the megaphone, while in a second embodiment an expansion chamber is provided of various effective size in accordance with engine operation. Manual control means is disclosed as a part of the system for accomplishing various positions, as well as a structure for controlling the state of the exhaust system in accordance with the position of the engine throttle.

Unite States atet [191 aczuk [451 Apr. 10, 1973 [54] VAABLE EUST SYSTEMFOR COUSTION ENGINE [76] Inventor: Richard Charles Raczuk, 17218 IndexStreet, Granada Hills, Calif. 91344 [22] Filed: Mar. 29, 1971 [21] Appl.No.: 128,770

[51] Int. Cl ..F01n 7/08 [58] Field of Search ..60/275, 312, 313,60/314; 123/65 E [56] References Cited UNITED STATES PATENTS 2,102,55912/1937 Kadenacy ..60/273 3,254,484 6/1966 Kopper ..60/275 2/1968 Tenney..60/3 14 5/1968 I-Ioltermann ..60/314 3/1969 Burkhart ..60/314 PrimaryExaminerDouglas Hart AttomeyNilsson, Robbins, Wills & Berliner ABSTRACTAn exhaust system is disclosed with movable elements to accommodatevarious operating states of an associated engine. In one embodiment adiverging megaphone faces a reflector which may be variously positionedin relation to the end of the megaphone, while in a second embodiment anexpansion chamber is provided of various effective size in accordancewith engine operation. Manual control means is disclosed as a part ofthe system for accomplishing various positions, as well as a structurefor controlling the state of the exhaust system in accordance with theposition of the engine throttle.

4 Claims, 5 Drawing Figures PATENTED APR 1 0 I975 3, 7 2 6 O 9 2 THROTTLE C 04/ TEOL CONTROL i R/CHAQD C. ,QAcZuK BY NILSSON, ROBBINS, WILLS &BEIZLINEQ l1 FTORNEVS VARIABLE EXHAUST SYSTEM FOR COMBUSTION ENGINEBACKGROUND AND SUMMARY OF THE INVENTION In the past, it has beenproposed to increase the performance of an internal-combustion,reciprocating engine by variously improving the exhaust system. Oneconcept has been to utilize pressure variations developed within anexhaust system to supplement the control for moving gases to improveengine performance. In effect, an exhaust system may develop some rathersubstantial pressures that are both positive and negative with referenceto ambient, and which pressures may be effectively utilized toaccomplish more desirable movement of gases through the engine.

Essentially, it is desirable to provide a negative pressure at theengine exhaust port during the interval when both the exhaust andtransfer ports are fully open, so as to more effectively draw a chargeof fresh gas into the cylinder. Subsequently, as the exhaust port closesit is desirable to provide a positive pressure to restore and maintainthe fresh charge of gas in the cylinder and initiate compression.Exhaust systems have been proposed for accomplishing such pressurevariations; however, design considerations tend to be exceedinglycomplex, and sizes are very critical in relation to specific engines andoperating conditions. The problems generally related to designingexhaust systems for internal combustion engines are perhaps moredifficult in relation to small engines, e.g., two cycle engines.Generally, applications for such engines involve a demand for highperformance yet, are so varied that flexibility is required.Furthermore, the inherent problems of design are compounded by reason ofnoise-control considerations and space limitations. Consequently, a needexists for an improved, more flexible exhaust system.

It has been'determined that the design considerations for an exhaustsystem include the operating speed of the engine. Generally, thesignificance of speed may be somewhat more apparent with the recognitionthat the exhaust system receives gas pulses, the frequency of which isdirectly related to the operating speed of the engine. Thus, a needexists for an exhaust system that may be more-uniformly used on smallengines, and which is capable of accomplishing improved operatingperformance at various engine speeds.

In general, the present invention is directed to an exhaust system, thecharacteristics of which may be varied to enhance performance of aparticular engine operating at a particular speed. Specifically, thesystem includes a chamber means, the walls of which define a chamberwith an intake opening (adapted to be connected to the exhaust port ofan engine) and an exhaust opening. The effective size of the chamber asprovided, may be varied in accordance with the operating speed of theassociated engine for improved performance.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which constitute apart of this specification, exemplary embodiments demonstrating variousobjectives and features hereof are set forth as follows:

FIG. 1 is a block and schematic diagram illustrative of a systemincorporating the present invention;

FIG. 2 is a partially sectioned side view of a specific embodiment of aportion of the system illustrated in FIG. 1;

FIG. 3 is a partially sectioned side view of an alternative structure tothat shown in FIG. 2;

FIG. 4 is a perspective view of a control unit as may be embodied in thesystem of FIG. 1; and

FIG. 5 is a vertical sectional view taken longitudinally through thestructure of FIG. 4.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS Referring initiallyto FIG. 1, an engine 10 is represented, the operating speed of which iscontrolled by a throttle 12. The engine 10 may comprise any of a varietyof two-cycle units, for example, and the throttle 12 may incorporate anyof a variety of well known mechanical or other control arrangements. Theexhaust port 14 of the engine 10, as indicated in FIG. 1, is connectedthrough a pipe 16 to an exhaust unit 18. As somewhat symbolicallyrepresented in FIG. 1, the exhaust unit 18 defines a chamber 20 ofvariable size between the pipe 16 and a tubular outlet 22. Specifically,the cylindrical portions of members 24 and 26 may be variouslytelescopically related by an exhaust control 28, to vary the effectivesize of the chamber 20.

Generally, it has been determined that the length of the chamber 20 isdesirably inversely related to the operating speed of the engine 10.Accordingly, the exhaust control 28 may be employed to move the member26 in either direction as indicated by an arrow 30 in accordance withthe operating speed of the engine 10. As indicated by a dashed line 32,the throttle 12 may be coupled to the exhaust control 28 to afford aunitary control. Alternatively, as described in greater detail below,the two controls may be completely independent.

Considering the operation of the exhaust unit 18 in somewhat greaterdetail, it has been determined that a cyclic pressure variation may bedeveloped in the pipe '16 that will improve the performance of theengine 10.

Generally, the pressure pulse of exhaust gases (discharged from theexhaust port 14 into the pipe 16, on combustion) is followed by apartial vacuum, somewhat as a wave pattern with reference to time. Asindicated above, the partial vacuum may be utilized to improve the flowof gases to charge a cylinder for another combustion. Additionally,improved performance also may be attained by terminating the partialvacuum at a time when the cylinder is fully charged. Accordingly, theexpansion chamber 20 develops a reflection or echo of the positivepressure to elevate the pressure in the pipe 16 when the cylinder ischarged, halting the flow of such fresh charge from the engine.

The frequency (and phase) of the pressure pulses from the engine 10 varywith the speed of the engine. Accordingly, the effective length of thechamber 20 is adjusted or tuned by the exhaust control 28 to preservethe desired timing relationship in the exhaust system. During high-speedoperation of the engine 10, the effective length of the chamber 20 isrelatively short to accomplish a short interval between pressure pulseand pressure reflection, or echo. Conversely, when the engine 10 isoperating at a low speed, the desired length of the chamber 20 iseffectively long, so that the reflection of increased pressure is notreturned to the pipe 16 until a longer interval of time has passed.Thus, the engine 10, in various forms, is effectively accommodated atvarious operating speeds.

Considering a more-detailed embodiment of the exhaust unit 18, referencewill now be made to FIG. 2 which shows a substantially cylindricalhousing 34 having an axial entry through a connection flange 36 and ashort tubular section 38. The flange 36 may incorporate variousconnectors as well known in the prior art for coupling the unit to theexhaust port of an engine.

The tubular section 38 is concentrically affixed in a circular wall 39of the housing 34 and is integral with a coaxial, somewhat conical,diverging megaphone or diffuser 40 positioned inside the housing 34. Theenlarged end 42 of the diffuser 40 terminates at a location that isspaced a substantial distance from the opposed circular wall 44 of thehousing 34. A collar 46 is centrally affixed in the wall 44 and matinglyreceives a sliding rod 48, the internal end of which carries a reflector50 of circular configuration and having a diameter to substantially matewith the inside diameter of the housing 34. The external end of the rod48 is connected to a control cable 52 which may be actuated as describedin detail below, to vary the effective size of the chamber 49 thatexists between the diffuser 40 and the opposing face of the reflector50.

The forward end wall 39 of the housing 34 also receives an axiallyoffset pipe 54 which incorporates two bends to change direction andextend as a length 56 toward the rear wall 44 of the housing 34. Thus,the path of exhaust gases through the unit of FIG. 2 is through theintake pipe 38, out of the diffuser 40 to be returned from the reflector50 and pass between the end 42 (of the diffuser 40) and the cylindricalwall 51 of the housing 34, and finally pass from the pipe 54.

In the operation of the unit of FIG. 2, the reflector 50 may bevariously spaced (by the cable 52) in relation to the end42 of thediffuser 40, which space defines the chamber 49 and is generallyinversely related to the operating speed of the engine. Accordingly, asconsidered above, the reflector 50 accomplishes an echo or reflectedpressure pulse in the tubular section 38 in timed relationship with theoperating speed of the associated engine, whereby to halt thedissipation of a fresh charge from the engine cylinder immediately priorto closure of the exhaust port (not shown). Furthermore, as indicatedabove, the elevated pressure initiates compression within the cylinder(not shown) and accordingly, improves performance of the engine.

Referring now to FIG. 3, another embodiment of the exhaust structure isrepresented somewhat as a variable-length expansion chamber. Generally,a conically ended housing 60 slidably receives a conical divergingmember 62 (shown in two positions, actual and phantom). As the divergingmember 62 is variously positioned along the length of the housing 60,the effective size of the chamber 64 is varied to attain the operationcharacteristics described above for a specific engine operating at aspecific speed.

The housing 60 includes an initial tubular length 66 for coupling theunit to the exhaust port (not shown) of an engine. Generally, the length66 may incorporate a flange as previously disclosed or various otherforms of fasteners as well known in the prior art. Alternatively, thelength 66 may simply be welded or otherwise integrally affixed toreceive exhaust gases from an internal combustion engine.

The tubular length 66 terminates in a diffusing or diverging length 68which is generally conical and may be integrally formed with the tubularlength 66. The housing 60 next includes a cylindrical length 70 which inturn terminates at a converging length 72 of generally conical shape,the small end of which is integral with a short collar 74.

The internal member 62 is coaxially affixed to an elongated tubularsection 76 which passes in sliding relationship through the collar 74.The external end of the tubular section 76 (remote from the length 70)carries a flange 78 defining an outlet port 80 and confining acompression coil spring 82 by engagement at an outward end. The inwardend of the coil spring 82 abuts the collar 74, so that as the springexpands to an uncompressed state, the internal conical member 62 isdrawn into mating engagement with the length 72 of the housing 60, asshown, thereby providing the greatest size for the expansion chamber 64.

A bracket 84 is affixed to the outside of the collar 74 and supports acable 86, the sliding internal wire 88 of which is attached to theflange 78 by a fastener 90. Thus, the diverging member 62 may be movedfrom a mating end position, as shown, to an internal position asindicated in phantom. One form of structure for moving the member 62through the cable 86 is disclosed in detail below.

The units as illustrated in FIGS. 2 and 3 may be variously manufacturedusing any of a wide variety of metal shaping techniques. Specifically,for example, with regard to the unit of FIG. 3, the lengths 66, 68 and70 may be formed as one integral component, as from stainless steel orother material while the length 72 and the collar 74 are separatelyformed as another component. The member 62 with the tubular section 76may then be fitted into the length 72, and the two separately formedcomponents (comprising the housing 60) may be affixed together as bywelding or other joining techniques.

In operation, the coil spring 82 urges the internal member 62 outwardlyto define a large effective chamber. As indicated above, this operatingconfiguration serves low-speed operation of an engine. The smallereffective chamber (existing when the member 62 is pushed inwardly)accommodates high-speed engine operation.

As indicated above, the means positioning the elements in the exhaustunits as depicted, may be a structure directly controlled by the enginethrottle. Alternatively, a separate control unit may be provided. Ofcourse, a wide variety of different control units are readily adaptableto afford the desired positioning; however, one such exemplary unit isillustrated in FIGS. 4 and 5 and will now be considered.

An end-closed cylindrical body 92 telescopically receives a sliding rod94 (FIG. 5) having a radially extending handle 96 which terminates in aknob 98. The handle 96 extends through an elongated, axially alignedslot 100 (FIG. 4) which is defined in the body 92. The slot incorporatesa plurality of transverse locking detents 102 for receiving the handle96 to establish a variety of locked positions.

The body 92 is rigidly supported as indicated by brackets 104 so that asthe rod 94 is variously positioned within the tubular space 95, a wire106 affixed to the rod 94 is variously positioned. The wire 106 extendsfrom the body 92 through a coupling108 which also receives a cablesheath 110 for guiding the wire 106 to the exhaust structure. Of course,a wide variety of different specific arrangements may be employedbetween the control unit and the exhaust unit. As depicted in FIGS. 4and 5, the wire 106 may be simply coupled to control the variableeffective length of the muffler unit, e.g., the wire 106 may becontinuous with the wire 88 (FIG. 3). Of course, various other designarrangements will also be readily apparent both in detailed structureand overall system; accordingly, the scope hereof is as set forth in theclaims as follows.

What is claimed is:

1. An exhaust system for a combustion engine, having an exhaust port,comprising:

a housing chamber including a conical diffusing section and an integralconcentric cylindrical section; means for coupling said conicaldiffusing section of said housing chamber to said exhaust port;

an internal conical member slidably received in said housing chamber infacing-opposed concentric relationship to said conical diffusingsection;

spring biasing means for urging said internal conical member whereby toseparate said member from said conical diffusing section; and

an actuator means for moving said internal conical member to variousrelative positions in said housing chamber for different operatingspeeds of said engine.

2. A system according to claim 1 wherein said internal conical memberfurther includes an elongate, integral concentric tube and wherein saidspring biasing means comprises a coil spring positioned on said tube forproviding a force between said tube and said housing chamber.

3. A system according to claim 1' wherein said actuator means comprisesa coupling from the throttle control of said engine to said internalconical member.

4. A system according to claim 1 wherein said actuator means comprises acylindrical body, a telescopic rod slidably received in said body, aradially extending handle affixed to said rod for locking engagementwith said body, and a cable extending from said rod to said internalconical member.

1. An exhaust system for a combustion engine, having an exhaust port,comprising: a housing chamber including a conical diffusing section andan integral concentric cylindrical section; means for coupling saidconical diffusing section of said housing chamber to said exhaust port;an internal conical member slidably received in said housing chamber infacing-opposed concentric relationship to said conical diffusingsection; spring biasing means for urging said internal conical memberwhereby to separate said member from said conical diffusing section; andan actuator means for moving said internal conical member to variousrelative positions in said housing chamber for different operatingspeeds of said engine.
 2. A system according to claim 1 wherein saidinternal conical member further inCludes an elongate, integralconcentric tube and wherein said spring biasing means comprises a coilspring positioned on said tube for providing a force between said tubeand said housing chamber.
 3. A system according to claim 1 wherein saidactuator means comprises a coupling from the throttle control of saidengine to said internal conical member.
 4. A system according to claim 1wherein said actuator means comprises a cylindrical body, a telescopicrod slidably received in said body, a radially extending handle affixedto said rod for locking engagement with said body, and a cable extendingfrom said rod to said internal conical member.